Field of the Invention
This invention relates to a foamable sodium percarbonate bleaching agent composition which foams vigorously in water and which has an excellent solution velocity and a long shelf life.
As clothes bleaching agents, there are known the oxygen-type and the chlorine-type bleaching agents. In Japan, chlorine-type bleaching agents which exhibit an excellent bleaching effect at a low temperature have come into general use. The chlorine-type bleaching agents are effective on cellulosic fibers but cannot be used for synthetic fibers, because they cause yellow stain damage to synthetic fibers and they decolorize dyed clothing made from synthetic fibers.
On the other hand, the oxygen-type bleaching agents have the advantages that they can be used for treating most synthetic fibers as well as cellulosic fibers, and they can be used safely for dyed clothes because of their mild bleaching action.
However, the oxygen-type bleaching agents, a typical example of which is sodium percarbonate, have only a poor solution velocity at low temperature and therefore a sufficient bleaching power cannot be obtained at such temperature. Further, because of their poor solution velocity the remaining undissolved particles of the oxygen-type bleaching agent adhere to the fibers to form local high concentration bleaching zones whereat the fibers are damaged and partial decolorization is caused. Thus, the oxygen-type bleaching agents, which are effective in clothes washing at a high temperature of above 60.degree. C, have not been used up to the present in Japan in those situations wherein washing is generally effected at a low temperature of about 20.degree. C. In view of these circumstances, improvement in the solution velocity of oxygen-type bleaching agents has been desired.
In bleaching agents containing sodium percarbonate as an active ingredient, a so-called "activating agent" is incorporated to increase the bleaching power of sodium percarbonate, because of its poor bleaching power at a low temperature. However, if an activating agent is incorporated in sodium percarbonate, the stability of the sodium percarbonate is impaired seriously. Particularly, if the bleaching agent is stored for a long period of time as in domestic usage, decomposition of the sodium percarbonate occurs thereby reducing the amount of available oxygen, whereby the composition eventually becomes unsuitable for practical use. Further, a caking problem occurs, and the decomposition of the sodium percarbonate causes an increase in the volume of the product and the container is thereby expanded or broken.